Power stop controls



NOV. 27, 1962 NEAL ETAL 3,065,518

POWER STOP CONTROLS Filed March 50, 1959 2 hee s-Sheet 1 Fig.1. 5

l3 i l6-\ m if 35 34 J 1 r II--' I B d" 4!] F an 42 22 v l I C as i J 1c A Py- B i r "1' 1 v INVENTORS RICHARD D. NEAL CARROLL W. CROMWELLJR BYwAz-m Nov. 27, 1962 Filed March 50, 1959 R. D. NEAL ETAL 3,065,518

POWER STOP CONTROLS 2 Sheets-Sheet 2 INVENTORS RICHARD D. NEAL CARROLLW. CROMWELL,JR

BY am ATT NE 3,065,518 POWER STGP CONTROLS Richard 1). Neal and CarrollW. Cromwell, Jr., Asheville, N.C., assignors to American EnkaCorporation, Erika, N.., a corporation of Delaware Filed Mar. 30, 1959,Ser. No. 803,002 14 Claims. (Cl. 285l) This invention relates in generalto the feeding of yarn, threads, strands, etc., of indefinite lengthsunder controlled conditions and more particularly to a novel means forinterrupting the feed in response to a sudden increase in tension on therunning yarn.

While not limited to such, the present invention is particularlyapplicable to the winding of a plurality of yarns into warp form on asingle beam or yarn take-up, and will be specifically described inconnection with that operation.

It is desirable, and practically essential from the standpoint ofsalability, that the plurality of ends forming a warp be collected onthe beam under uniform conditions. Any increase in tension on any one ofthese ends will cause uneven winding at the take-up means, whichintroduces difficult handling problems in subsequent processing of thepackaged yarn. Sudden increases in tension are generally caused byirregularities in formation of the cakes, cones, or other yarn packageswhich supply singles to the warping creel. In yarn supplied from cakes,for example, plucks are often formed from uneven shrinkage of the cakesduring washing and drying. Additionally, defects may be produced fromoverwinds or underwinds during initial supply package formation, oruneven distribution of finish on the yarn may produce tension increasesbecause of the resulting variation in friction.

The warp forming problem described briefly above is well known in thetextile field. Moreover, many attempts have been made to obviate thisproblem by detecting any sudden increase in tension and automaticallyinterrupting yarn feed in response thereto. These known stop motion orknock-off devices generally employ either the normal effect of gravityon a weighted member, or spring-biased levers, or both. Such devices aredesigned to stop the feed of yarn immediately upon increase in yarntension to a given level so that the cause of tension increase may belocated and corrected before continuing collection of the yarn.

While the known stop motion devices are theoretically sound, there aremany disadvantages to operation of the same. With a device utilizing thespring bias principle, for example, each operating position must be setindividually. A standard warper creel employes thousands of yarn ends,and yarn control positions, which means that a considerable amount ofman hours is required for initial setting of the controls. Moreover, thesprings weaken and the settings accordingly drift upon extended use,which means that a substantial amount of time is required to maintainthe controls in proper adjust-ment.

The stop motion devices of the gravity type usually employ a weight orweighted arm which counterbalances tension in the running yarn and whichis displaced in response to tension variations to interrupt the yarnfeed motor circuit. Inasmuch as the inertia of the weight or weightedarm must be overcome before any shifting can result, these devices haveproved less sensitive to change in tension than required in commercialoperations to protect the physical and chemical characteristics of theyarn. In other words, the mass necessary to counterbalance runningtension in the yarn inherently reduces sensitivity and precludesimmediate activation in response to tension variation. Anotherdisadvantage of the grav- 3,%5 ,5 l8 Patented Nov. 27, 1962 igC itymechanism is that each device of the thousands employed must be setindividually.

One of the primary objects of this invention is to provide a stopmotion, or knock-off device for running yarn not having thedisadvantages of known systems such as described above.

Another object of the present invention is to provide a stop motionsystem affording simultaneous and equal tension level adjustment of aplurality of units.

Still another object of this invention is to provide a stop motiondevice for running yarn which may be easily and quickly adjusted todesired knock-off tension, and which will maintain the initial tensionlevel until subsequently readjusted.

A further object of the present invention is to provide a stop motiondevice which requires a minimum of servlClIlg.

An additional object of this invention is to provide a low passknock-off device having very little inertia and internal friction andwhich may be activated immediately upon increase in tension to apredetermined level on yarn running therethrough.

Another object of the present invention is to provide a stop motiondevice which is adjustable over a wide range of tensions in order toaccommodate various types of running yarn.

Still another object of this invention is to provide a stop motiondevice which also functions to impart desired tension to running yarn.

A further object of the present invention is to provide a novelelectromagnetic yarn tensioning device which also operates to interruptyarn feed immediately upon increase in tension above a predeterminedlevel.

A more specific object of this invention is to provide anelectromagnetic warp tension device which will uniformly tension aplurality of yarns fed to a warping machine and which will interruptoperation of the warping machine immediately upon increase in tension onany of the running lengths of yarn.

The foregoing objects may be accomplished in accordance with the presentinvention by utilizing a normally energized electromagnetic device formaintaining a secondary or control circuit in an inactive or inoperativestate, by displacing running yarn laterally from an establishedrectilinear path in operative contact with said device so that at leasta component of the yarn tension tends to render said secondary circuitoperative, but is unable to do so until the electromagnetic force isovercome, by suitably connecting said secondary circuit to the primaryyarn feed motor circuit so that actuation of the former will interruptthe latter, and by adjusting the voltage in the coil of theelectromagnetic device so that the force developed thereby willcorrespond with, or counterbalance, normal yarn tension. An increase inyarn tension above the adjusted level will immediately unbalance thesystem, or overcome the electromagnetic force, and render the secondarycircuit operative, which will interrupt the primary circuit andinstantaneously discontinue the feeding operation. It is preferred thatthe force developed by the energized electromagnetic device also beutilized to impart primary tension to the running yarn.

Gther objects and advantages will become apparent upon study of thefollowing detailed disclosure taken in conjunction with the accompanyingdrawings, wherein FIGURE 1 is a circuit diagram illustratingschematically a series or group of electromagnetic stop motion devices,a secondary or control circuit activated thereby, and a normally closedfeed motor circuit which is opened in response to activation of thesecondary circuit;

FIGURE 2 is an elevational view, partly in section and partly schematic,showing the passage of yarn from a supply source to a war-ping beam, andillustrating a preferred stop motion device which also functions totension yarn;

FIGURE 3 is an elevational view of an alternative stop motion devicewhich functions only to interrupt the feed of yarn passing therethroughin response to increase in yarn tension; and 1 FIGURE 4 is a perspectiveview of the combination stop motion-tension device showndiagrammatically in FIGURES 1 and 2.

The component parts of a single combination stop motion-primary tensiondevice will now be described with particular attention to FIGURES 2 and4, it being understood that corresponding elements will be identified bylike reference numerals throughout the specification and drawings.Moreover, it should also be understood that the additional devices 11and 12 shown in FIGURE 1 may be and preferably are of identicalconstruction to the device 10. i

The device 10 consists of an electromagnetic head 13 which may bemounted in any convenient manner to subframe 14. The sub-frame in turnis supported by a warper creel (not shown) or any other framework withwhich the device is to be used. Electromagnetic head 13, which containsa coil or winding (not shown), is commercially available and will not bedescribed in detail. Mounting post 15 is fixed to and extends normalfrom the plane of the coil enclosed within head 13 and, in thisembodiment, supports head 13 from sub-frame 14.

An apertured tension disc 16 formed from magnetic material is slidablyand rotatably mounted over post 15. In the modification presentlydescribed, this disc performs a dual function. Upon inspection of FIGURE2, it will be seen that the yarn or thread 17 to be controlled passesbetween the disc 16 and head 13. When the coil within head 13 isenergized, disc 16 is urged against yarn 17, which produces a frictionaldrag or resistance to passage, thereby imparting considerable tension,depending on energization of the coil. The disc 16 also is conductive,and serves the additional function of activating a secondary or controlcircuit now to be described.

Attention is directed to the fact that electromagnetic head 13 ismounted in an inverted position from that heretofore suggested. Withthis mounting the normal effect of gravity is utilized to urge the discaway from the head. Although this arrangement is not essential from atheoretical standpoint, the same, practically speaking, is veryimportant to the present invention. Displacement of disc 16 away fromhead 13 activates the secondary circuit, as will be more fully explainedinfra. An undesired increase in yarn tension is used to physicallydisplace the disc. It is necessary, therefore, that the weight of thisdisc be kept at a minimum, else too great a knock-off tension would berequired to overcome the inertia thereof. If a substantially weightlessdisc could be obtained, a slight increase in yarn tension would besufficient to displace the same, and the head 13 could be mounted in anyposition desired. Since weightless discs are not available, however, ithas been found that the force of gravity should be utilized to assistdisc knock-off and reduce that increased yarn tension required tointerrupt the yarn feed motor circuit. A more satisfactory operationthus is obtained, since the sensitivity of the stop motion device isinversely proportionalto the incremental tension required to displacedisc 16.

With attention now directed to FIGURES 1 and 2, it can be seen that fourindependent but definitely interrelated circuits have been illustrated.Reference letter A represents a steady or pulsating source, orcombination of both, of direct or alternating current used solely forenergizing the coils within. electromagnetic heads 10, 11 and 12. Theseheads are wired in parallel to power leads 18, 26 in this embodiment,although it should be understood that a series connection could beusedequally effectively. A potentiometer 21 is advantageously providedintermediate the coils and source of current A to enable simultaneousand uniform adjustment of the force generated by each of the heads 10,11,12. If simultaneous adjustment is not desired, individualpotentiometers could of course be provided for each head. This forcedetermines not only the primary tension imparted to the running yarn 17but also the amount of additional or knock-off tension required toinactivate the feed of yarn. Usually, from 15 to 250 ma. current, atfrom 1 to 20 volts, is sufficient for the purposes described.

Reference letter,B represents, and may also be used to identify thesource'of current provided for, the secondary or control circuit. Thissecondary circuit is utilized to energize relay 22 which, uponenergization, opens the primary yarn feed motor circuit indicated at C.Power leads 2.3, 24, which form the secondary circuit B, connect at oneend to a suitable source of current such as 6.3 volts, alternating ordirect, and connect at the opposite ends to additional stopmotion-tension devices, neither of which are shown.

Primary circuit C is represented by power leads 25, 26 which supply yarnfeed motor 27 with either or 220 v. A.C., depending upon the type ofprocessing to which yarn 17 is subjected. This circuit as shown isprovided with two relay-operated switches 28, 30, to be described morefully hereinafter, and a manual on-off switch 31. It should beunderstood, however, that additional switches 28 will be required,onefor each of the stop motion tension systems provided. One completesystem, as used here, .is represented by a plurality of individual unitsor devices such as 10, 11, 12. Moreover, where cost and spacerequirements are of no consequence, it may be practicable to provide arelay 22 for each of the devices 10, 11, 12. It has been foundexpedient, however, to wire the system in such a manner that a pluralityof devices operate the same relay. Although three of these devicesoperate relay 22 in the diagram illustrated, it will be apparent thatany other number could be connected in the manner described; It willbecome obvious hereinafter, however, that the most desirable arrangementwould employ one relay 22 for each stop motion-tension device.

Returning for the moment to FIGURE 1, the fourth independent butinterrelated circuit is represented by reference letter D. This circuitis provided on a conventional warping machine for the purpose ofinterrupting the warping operation immediately upon determination thatone or more of the ends or filaments fed to the collecting beam has beenbroken. The break detector circuit D may employ a photo-electric scannerand receiver placed on opposite sides of the, warp, or drop wire stopmotion, or any known system indicated simply by numeral 32 in FIGURE 2,and operatively connected to a relay such as 33 (see also FIGURE 1).Upon detection of a broken filamentor end, the unit 32 functions toenergize relay 33 and thereby open switch 30, which interrupts yarn feedimmediately. This circuit, per se, forms no part of the presentinvention and is included here merely to illustrate that the novel stopmotion system which constitutes the subject matter of this applicationis supplementary to, and not in lieu of, known mechanisms for openingfeed motor circuits in response to yarn breakage. It can be seen fromthese figures that both secondary or control circuit B and breakdetector'circuit D are operatively connected to, and function to open,the primary or yarn feed motor circuit C.

A pair of contacts 34, ,35 is associated with each of the devices 10,11, 12, and the discs 16 mounted on the posts 15 thereof. These contactsmay be supported in an insulated condition from a sub-frame 14, asshown, or in any other manner desired. Contact 34 is connected throughconductor 36 to power lead 24 of control circuit B, as illustrated inFIGURE 1,-while contact 35 is connected through conductor 37 and pilotlight 38 to the remaining power lead 23 of circuit B. Relay 2,2 is Wiredthrough conductors 40, 41 in parallel with the pilot light andconsequently is operated simul taneously therewith. It can be seen fromthis circuit diagram that displacement of disc 16 results inenergization of relay 22 and concomitant interruption of primary circuitC.

Increased yarn tension of any magnitude or duration above apredetermined level is detrimental to the warping operation.Consequently, it is desired that even a momentary tension increase abovethe knock-01f level be detected and the cause of such be corrected priorto resuming yarn feed. While a sudden increase of short duration mighttemporarily dislodge one side of disc 16 sutficiently to short outcontacts 34, 35, such momentary increases usually would not completelydisplace the disc from head 13, and primary circuit C would beinteirupted temporarily only unless other measures were taken.Accordingly, a lock-in circuit consisting of switch 42 and conductor 43is provided to lock relay 22 in energized condition from a momentaryshorting only of contacts 34, 35. The result of this lock-in issustained inactivation of the primary circuit C (until manually reset)even from a brushing of contacts 34, 35 by disc 16.

The secondary circuit B operates in the following manner. Closing ofcontacts 34, 35 establishes continuity from power lead 24 throughconductors 36, 37, and 41 to relay 22, and from this relay throughconnector 40 to the remaining power lead 23. A circuit also is completedthrough pilot light 38 which locates the source of diificulty for thecreel operator. Energization of relay 22 from leads 23, 24 operates toshift switch 28 to open position, thereby interrupting primary circuitC. The normally open lock-in switch 42, Which is mechanically connectedto switch 28, is shifted to closed position, thereby establishing thelock-in circuit through conductors 43, 40. Subsequent opening of thecontacts 34, 35 therefore will not reactivate the primary circuit C.Consequently, even though the tension increase on yarn 17 might havebeen of a momentary nature only, yarn feed will be discontinued untilthe source of difiiculty can be located and obviated.

After correction of the tension problem the stop motion-tension systemmust be reset so that yarn feed may be resumed. This may be accomplishedby temporarily opening normally closed reset switch 44. It will beobvious, however, that disc 16 must be restored to operative positionprior to resetting, if the same has been completely displaced from themagnetic field within head 13 by the increase in 'yarn tension.

Operation of the preferred embodiment will now be summarized withparticular attention to FIGURE 2, which figure shows only enough detailsof the circuit to enable a complete understanding of this invention.Yarn is withdrawn from a supply package 45 by take-up means 46 which, inthis instance, is a beam for collecting a warp of individual ends.Although only one end is shown in FIGURE 2, it will be understood that aplurality of yarns 17, and a plurality of stop motiontension devices arerequired to fill beam 46. Beam 46 is driven by motor 27 in a mannerknown to this art. Moreover, the operation of photo-electric scanner andreceiver 32 also is known and will not be described further.

Yarn 17 may be passed through a preliminary tension device 47,electromagnetic or otherwise, if found to be necessary or desirable,after which it is introduced into the stop motion-tension unit 10 in aplane parallel to the face of head 13. Usually the yarn passes about 270about mounting post 15, as illustrated in FIGURE 4, before dischargingtherefrom. As stated earlier, yarn 17 passes between disc 16 and head 13so that the magnetic force urging the disc against the head will alsoserve to tension the yarn. The disc 16 usually rotates during operation,which promotes uniformity of tension.

It is essential that yarn 17 be introduced and/or withdrawn from thedevice it in such a manner that at least a component of the tensionalforce developed therein will function to urge disc 16 away from head 13.

'48 mounted so that the yarn extending between it and the disc 16 formsan angle alpha with an imaginary horizontal plane, or with the plane ofyarn running from guide 48 to the warper. The knock-elf tension leveland the ratio of yarn tension to knock-off tension are dependent uponthe magnitude of angle alpha. Although an angle alpha of between 35 and40 degrees has proved satisfactory for most purposes, the angletheoretically may lie anywhere between about 1 and degrees. It ispreferred that guide 48 be adjustably mounted, as indicated by thearrow, so that this angle may be changed when desired to accommodatevarious types of yarns, various yarn tensions, and various ratios ofprimary tension to knock-off tension.

In some operations it might be desirable not only to withdraw yarn frombut also to introduce the same to device 10 at an angle. Accordingly,thread guide 50, which may also be adjustably mounted as indicated bythe arrow, has been provided to deflect yarn from supply package 45through the dashed line path to the stop motion-tension device. Theangle of approach, beta, is determined by the same conditions as, andmay correspond generally to, the angle alpha discussed above.

A modification of the device described hereinabove will now be discussedwith attention directed to FIG- URE 3. As can be seen from an inspectionof that figure, the stop motion or knock-0E device 51 functions only tointerrupt operation of the yarn feed motor circuit and does notdirectly, or primarily, tension the running yarn. Stop motion device 51is provided with an electromagnetic head 13, similar to that used withthe previously described embodiment except for a central aperture, whichis electrically connected to the source of current A either in series orparallel with additional devices. This unit difliers slightly from thedevice shown in FIGURE 4, however, in that mounting post 52 is supportedfor limited longitudinal movement through the aperture head 13 andrelative to the coil (not shown) enclosed thereby.

A washer 53 of magnetic material is fixed to post 52 and limits upwardmovement, whereas an electrical disclike contact 54 fixed to the upperend of post 52 limits downward movement. The movable contact 54cooperates with stationary contact 55, which is fixed to the upper sideof head 13, to activate or close control circuit B, indicated in thisfigure only by a bracket. The lower end of post 52 terminates in athread guide 56 through which yarn 17 is passed, either at an angle betafrom guide 50, as indicated in solid lines, or normal to the mountedpost, as indicated in dotted lines. The yarn is withdrawn from guide 56at an angle alpha and passed, under guide 48. The two positioning guides48, 50 correspond to the identical guides described above. The head 13may be stationarily supported on a subframe (not shown) similar to 14shown in FIGURE 4. A separate tension device 57, which may beelectromagnetic or otherwise, is provided for imparting running tensionto the yarn 17.

Except for the single rather than dual function, device 51 operatesquite similar to devices 10, 11 and 12. Yarn 17 is withdrawn from asupply package such as 45 by feeding or collecting means such as beam 46(see FIG- URE 2). The yarn passes from the supply package through thetension device 57, under guide 50 (if angular introduction is desired),through guide 56 on mounting post 52, and under guide 48. The coilwithin head 13 is energized from circuit A, and the magnetic attractionresulting from this raises post 52 until washer 53 rests aaginst thelower side of the head. In this position contacts 54, 55 are separated,as shown, and control circuit B is inoperative. The force generated tomaintain post 52 in a raised position may be adjusted through apotentiometer such as 21, FIGURE 1, which of course deterthe samefunction.

of head 13. The axial spacing of washer 53 and movable contact 54 is sochosen that a slight downward movement of washer 53 will result inclosing the circuit B through contacts 54, 55. Activation of circuit Bresults .in interrupting yarn feed means circuit C in the same mannerdiscussed with respect to FIGURE 1. Preferably, the magnetic forceurging post 52 upwardly should exactly counterbalance the verticalcomponent of tension in the running yarn coupled with the effect ofgravity on the movable elements. As a result of this, any increase intension on the running yarn will increase the vertical component offorce represented by the arrow, and unbalance the system. A suitablelock-in circuit and reset switch should be provided. Consequently, evena momen-tary unbalance is sufficient to inactivate circuit C, asexplained earlier.

There are many alternatives to the preferred arrangements describedsupra. The angle of approach and discharge of yarn to the stopmotion-tension device is unlimited insofar as concerns tensioning, andany angle from about 1 to 90 is satisfactory for knock-off purposes,depending upon tensions, breaking strength, etc, mentioned above.Moreover, any positioning of the device should result in satisfactoryoperation as long as an incremental increase in tension in sufficient todisplace the secondary circuit activating means 16 or 54, 55. As statedabove, however, it is more practical to mount head 13 in an invertedposition so that the normal force of gravity will assist tensionincrease in shifting means 16 or 54, 55. Quick activation of controlcircuit B is obtained through use of an electromagnetic head 13 becausethe force acting on means 16 or 54, 55 decreases very rapidly, or inproportion to the square of the distance of this means from the head 13.Consequently, gravity, tension and decreased magnetic force contributemutually to quick operation of the circuit B Whenever the preset knock-dtension level is exceeded.

' It may be desirable in some instances to provide a pulsating currentfor energizing circuit A. This pulsating current of coursewill vary fromhigh current to low current periodically. With proper circuit design, itshould be possible to utilize the average of high and low current fortension purposes, while permitting knock-01f only at the low portion ofpulses, thereby enabling a more slight incremental increase to produceinterruption of circuit C. With either steady or pulsating currentsupplied to electromagnetic heads 13, however, the knock-off tensionrange may be varied through potentiometer 21 from a fractional gram toseveral times the primary tension imparted to the running yarn.Moreover, in certain operationsit may also be desirable to introduceyarn to the control unit at an angle and to withdraw the yarn therefromin a plane parallel to the tensioning head. With such an arrangement aneven slighter percentage tension increase should activate controlcircuit B since the primary yarn tension is lower at the introductionside than at the Withdrawal side.

Additionally, it may be desired to utilize one electromagnetic coil forstop motion purposes and another coil for tensioning. Such anarrangement would correspond to that shown in FIGURE 3, with device 57being an electromagnetic tensioning head. This system has the ing post,whereas the preferred arrangement shown in FIGURE 2 requires onlyonepost for both stop motion and tension control. 7 w

Although a conventional circular disc has been described in connectionwith the preferred embodimenn it is of course obvious that any type'ofmagnetic armature, such as a flat plate, apertured or otherwise, would'serve Moreover, contacts 34, 35 were selected primarily forillustrative purposes and other means,

such as microswitches, could be used equally advanta- 16 whilepreventing play therebetween, it may be found necessary to reduce thediameter of the post 15 immediately below' the normal operating positionof the disc. This construction also would permit slight pivotal movementof the disc about either a real "or imaginary pivot point, which wouldenable activation of secondary circuit B from an even slighter increasein tension.

While the stop motion-tensioning devices illustrated herein have beendescribed particularly in connection with a warping operation, it willbe apparent that the same could be used with any yarn feeding processsuch as coning, rewinding, draw-twisting, etc. Moreover, the inventionwill operate equally etfectively with any typefiber, whether the same benatural, artificial or synthetic, and fibers of any denier and/orbreaking strength may be controlled by proper manipulation ofpotentiometer 21.

Inasmuch as other alternatives will become obvious to those skilled inthis art, it is intended that the present invention be limited in scopeonly to the extent set forth in the following claims.

What is claimed is:

l. A power stop control comprising an apertured electromagnetic head,means permitting adjustable energization of said head, an elongatedmounting post positioned within the aperture of said head and movablebetween an operative and an inoperative position, said post normallybeing held in operative position by the magnetic force of said head, afirst electrical contact supported by one end of said post, a secondelectrical contact supported by said head, and a control circuitenergized by closing of said electrical contacts upon movement of saidmounting post from operative to inoperative position.

2. In combination with a warping operation having means for withdrawinga plurality of yarns through a rectilinear path, a plurality ofapertured electromagnetic heads, means for adjustably energizing saidheads, an elongated mounting post having a thread guide on one endthereof positioned Within the aperture of each head and movable betweenan operative and an inoperative position, said posts normally being heldin operative position by the magnetic end of each mounting post, saidthread guides functioning in operative position of said mounting post todisplace said yarns laterally from said rectilinear path while ininoperative position of said post permitting limited lateral movementtoward said path, a first electrical contact fixed to the other end ofeach mounting post, a cooperating second electrical contact fixed toeach of said heads, and a control circuit common to all of said contactsand operative upon closing of any cooperating pair thereof upon movementof said post to inoperative position for interrupting the feed of yarn,whereby an undesired increase in tension on any single yarn fed mayinstantly terminate said warping operation.

3. A warping operation as set forth in claim 2 and further includingmeans for individually tensioning said yarns prior to passage throughthe thread guides on respective mounting posts.

4. A power stop control comprising an electromagnetic yarn tensioninghead, a mounting post extending from said head, an apertured tensioningdisc slidably mounted between operative and inoperaive positions on saidpost, means for energizing said electromagnetic head and urging saiddisc into operative poistion, and a control circuit energized inresponse to movement of said tensioning disc into inoperative position.

5. A power stop control comprising a sub-frame, an electro-mag etic yarntensioning head supported on said sub-frame, a mounting post extendingfrom said head, an apertured tensioning disc slidably mounted betweenoperative and inoperative positions on said post, means for energizingsaid electromagnetic head and for urging said disc into operativeposition, a pair of normally open electrical contacts supported by saidsub-frame adjacent to said tensioning disc and adapted tobe closed uponmovement of said disc to inoperative position, and a control circuitoperative in response to closing of said contacts by said tensioningdisc.

6 A stop motion-tensioning system comprising a plur'ality ofelectromagetic yarn tensioning heads, a mounting post secured to andextending from each of said heads, an apertured tensioning disc slidablymounted between operative and inoperative positions on each of saidposts, means for simultaneously adjustably energizing saidelectromagnetic heads and urging said discs into operative positionagainst respective heads, a pair of contacts positioned adjacent eachdisc and adapted to be closed upon shifting of a respective disc intoinoperative position, a normally energized primary circuit the functionof which is to be controlled, a control circuit common to all tensioningheads and activated upon closing of any pair of contacts forinterrupting said primary circuit, and means including said tensioningdiscs for energizing said control circuit and thereby interrupting saidprimary circuit.

7. In combination with a yarn processing device having means for feedingyarn through a rectilinear path, a stop motion-tensioning devicecomprising an electromagnetic tensioning head mounted laterally of saidrectilinear path a mounting post extending from said head in thedirection of said path, an apertured tensioning disc slidably supportedon said post between operative and inoperative positions, said disc inoperative position tensioning said yarn and displacing the samelaterally outside said path, means for energizing said head and urgingsaid disc into operative position, a pair of electrical contacts mountedadjacent said post and adapted to be closed upon move ment of said discinto inoperative position, a normally deenergized control circuitconnected to said contacts and adapted to interrupt the feed of yarnupon activation thereof, and means for adjusting the energization ofsaid head to a predetermined tension level whereby an increase in yarntension thereabove will shift said disc into inoperative position, closesaid pair of contacts, activate said control circuit and interrupt thefeed of yarn.

8. A stop motion-tensioning device as set forth in claim 7 and furthercomprising means operating upon activation of said control circuit forvisually indicating the condition of that circuit.

9. A stop motion-tensioning device as set forth in claim 7 and furthercomprising a lock-in circuit whereby only temporary closing of said pairof contacts will interrupt the feed of yarn until the control circuit ismanually deenergized.

10. In combination with a warping operation having means for withdrawinga plurality of yarns through a rectilinear path and collecting the sameon a beam, a plurality of electromagnetic tensioning heads laterallydisplaced from said rectilinear path, a mounting post extending towardsaid path from each of said heads, an apertured tensioning disc slidablysupported on each of said posts between an operative and an inoperativeposition, each disc in operative position tensioning a single yarn anddisplacing the same laterally outside said path, means forsimultaneously energizing said heads and urging said discs intooperative position, a pair of electrical contacts mounted adjacent eachpost and adapted to be closed upon movement of a respective disc intoinoperative position, a normally de-energized control circuit connectedto each pair of contacts and adapted to interrupt the feed of yarn uponactivation thereof, and means for simultaneously adjusting theenergization of said heads to a predetermined tension level whereby anincrease in tension on any single yarn above this level will shift adisc into inoperative position, close a corresponding pair of contacts,activate said control circuit and interrupt he feed of yarn.

11. In combination, an electromagnetic tensioning head, a yarntensioning disc normally urged by magnetic force toward said head fortensioning yarn passed therebetween, means for feeding yarn between saiddisc and head and for withdrawing the same therefrom at an angle,electrical means for controlling the tension imparted to said yarn bysaid disc and head, and means operating in response to tension increaseabove the control level for interrupting the feed of yarn.

12. The device as set forth in claim 11 wherein said yarn is alsointroduced to the tensioning head at an angle.

13. A power stop control comprising a sub-frame, an electromagnetic yarntensioning head supported on said sub-frame, a mounting post extendingfrom said head, an apertured tensioning disc slidably mounted betweenoperative and inoperative positions on said post, means permittingenergization of said electromagnetic head for urging said disc intooperative position, and a pair of normally open electrical contactssupported by said subframe adjacent to said tensioning disc and adaptedto be closed upon movement of said disc to inoperative position foractivating a control circuit.

14. A power stop control comprising an electromagnetic yarn tensioninghead, a mounting post secured to and extending outwardly from saidelectromagnetic head, an apertured tensioning disc of magnetizablematerial supported by and slidably mounted on said post between anoperative position adjacent said electromagnetic head and an inoperativeposition remote from said electromagnetic head, power leads permittingenergization of said electromagnetic head resulting in retention throughelectromagnetic force of said tensioning disc in operative positionadjacent said electromagnetic head, and switch means supported adjacentsaid mounting post opposite said tensioning disc from saidelectromagnetic head for inactivating a control circuit in response tomovement of said tensioning disc into an inoperative position whilepermitting activation of said control circuit when said tensioning discis maintained in operative position by energization of saidelectromagnetic head.

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